Hot-moldable compositions and molded products



Patented Feb. 13, 1951 Y A,

w1U-N1111i!) STATES, PATENT OFHCE Hor-MOLDABLE coMPosI'rIoNs MOLDED PrgoDUcTs ,Y .Y Edward L. Krona, 01d Greenwich', Conn., and 'Joh'n Piunne, Richmond Hill, N. YL; assignors to *American Gyana-mid Company," New' York ygacorporation of Maine Non@ "'Ailiglgafion 'october 16, 1947, ASe 'al`N0. 7750,29'1 (Cl. 260-39) 3 Simms! 1 1 2 This invention relates to new and useful hotpositions the melamine-formaldehyde resin is in mqidme*(hop-'101531111519*composition "-ndfto ajcuedstate r v H Y ze se. lrbductjsie r'pris-ing thefimldd '('shedk'on- Molding (moldable) compositions containing a. sitinsF-MOe particulrlifith Vvini/erltioxifis heatfcurable (heat-convertible) melaniin'efrmi- 'lialgenated La'c'etamide; nr of ractillprfd? u cts of ingredients Leo mprising an'aminotriazine melamine; Aan 'aldehy'de 'e- .gq formaldehi' 'and Vcertain halogenated: nitrles,Y halogenate'd idesjofhfalogenated acetonesp I-Ioweverltofthg joi'sugfgested vpriort'o our invention thatsurbrstan Qtially'fhonogeneous, hot-moldable compositions., Whichfjin be formedfasfby molding,V Vextru ng, c endring, 4'etfcpj to' yield knroduci'l's comprising "a d, modi''ed melaminedornaldehyde' 'resin v v l y ng improved properties, could be obtained by a D St thereiorwnsistingfoi '7; 5`pats i'xing 'oriblending e; g., under heat, (1) ffby weight of'nor'rn li soliduhronolyrneized a onitril'e or'a'thermoplastic'copolymer l acrylonitrile nto eachzzs parts of the resinous lmingia't estabut 2.5%by Weght'iheof? iqlr'o'cluct; and morepm-ucularly `t a eomnosiuon gcryipnimle cpmpmedwherem sind' (zwanen- Which is moldajole under heat andfwhich is a 45 v12111111able,jrielamineformaldehyde resin asilo" dly substapuauy hgmogeneousblend of the `follow- ;ias ripeatirnrtherst paragraphof this sp1@ i, l- :i'gingredientsin'partos by Weight: itilnadmore'gfullyhereafter: or I t"tiveftionislbased on our discovery i225 ,that'thenfw stic-product'slofpolymeriia ',7-5 5G Qt'lie kind de o beds'in the rsi'rparagraph ofI 1, "speciatiobarijb incorporated intoiilled r unfilled compositis"Coriprising a,Vr heati'curab'le (thermosetting) melamine-formaldehyde resin to yield substantially homogeneous molding (mold- 55 iafble) 5compositions which lcan be molded (Shaped) Heat-curable melamine-formaldehyde resin- 2 oldfed 'prod-v for Texau'nle,"out standing 4resistance to vlriai'/ and 3. under heat to produce molded articles that are tougher and more elastic than the unmodified melamine-formaldehyde composition, while at the same time maintaining the good electrical and other useful properties characteristic of the melamine-formaldehyde resin. The acrylonitrile polymer or coplymer should be employed in a ratio, by Weight, corresponding to not less than approximately parts thereof for each 95 parts of the heat-curable melamine-formaldehyde resin in order to effect a material improvement in the toughness of the molded product. On the other hand, the arylonitrile polymerization product should not be used in a ratio, by Weight, exceeding approximately 55 parts thereof for each 45 parts of the heat-curable melamine-formaldehyde resin, since otherwise the composition yis lacking in the desired molding and curing characteristics, and the physical and electrical properties of the molded product are materially impaired as compared with a product similarly made from an unmodied melamine-formaldehyde molding composition.

Good results are obtained with hot-moldable compositions which are substantially homogeneous blends of ingredients comprising (1) a heat-curable melamine-formaldehyde resin and (2) a thermoplastic product of polymerization of a polymerizable vmass containing n-ot less than about 50% by weight thereof of acrylonitrile, the ingredients of (1) and (2) being present in such compositions in the ratio of, by weight, from 50 to 85 parts of the former to from 50 to 15 parts of the latter. The thermopastic p'olymerization product in our new compositions imparts toughness to the molded composition containing the melamine-formaldehyde resin which has been heat-blended with the polymerization product and ultimately cured in its presence during molding. During heat-blending of the melamineformaldehyde resin and the polymerization product, or during molding of the resulting moldable composition, or during both such steps, it is possible that co-reaction between the aforementioned ingredients may take place,

-It was quite surprising and unexpected that polymers and copolymers of acrylonitrile of the kind described in the first paragraph of this specification could be compounded, as by dry blending followed by hot milling, with a heatcurable melamine-formaldehyde resin in the presence or absence of llers and other conventional components of molding compositions, especially since such polymerization products, e. g., polyacrylonitrile of high molecular weight, are generally considered to be intractable materials that can be softened only at very high temperatures and pressures, Furthermore, such polymerization products, specifically those containing at least about 65% by weight thereof of acrylonitrile, are soluble in only a relatively few solvents. Hence it would not be expected and could not be predicted that substantially homogeneous compositions could be obtained by hot blending a polymerization product of the kind with which our invention is concerned and a heat-curable melamine-formaldehyde resin. It is believed that these results are obtained because of the ainity between the nitrile (-CN) groups in the polymer undergo polymerization reactions at elevated temperatures, and hence during hot blending of the polymeric or copolymeric acrylonitrile with the melamine-formaldehyde resin the former, which may be represented by Rf-CN where R represents the polymer residue, may undergo further polymerization through the nitrle groups to yield a polymer represented by which is more compatible or more easily dispersed in the heat-curable melamine resin than the starting polymerizationproduct.

In carrying our invention into eiect a polymer or copolymer (thermoplastic copolymer) of acrylonitrile is prepared in accordance with methods now well known to those skilled in the art. In the preparation of copolymers= a mixture of monomers comprising, by weight,` at least about,

25% and preferably not less than 40 or 50% of acrylonitrile is employed. monomeric mixture may contain from 60% to 99.5% by weight of acrylonitrile. f

Illustrative examples of monomers which may be copoymerized with acrylonitrile in proportions such as have been mentioned above to form a copolymer, more particularly a thermoplastic copolymer, are compounds containing a single- CH2=C grouping, for instance the vinyl estersand especially the Vinyl esters of saturated aliphatic'monocarboxylic acids, e. g., vinyl acetate, vinyl propionate, vinyl butyrate, etc.; vinyl-substituted (monovinyl-substituted) aromatic compounds, for instance styrene and the various nuclearly substituted styrenes (e. g., the Various' monoand dimethyl styrenes, the chloro, fluoro and other halogeno styrenes, the cyano styrenes,

etc.) a, p-dimethyl styrene (isopropenyl toluene) acrylonitrile polymer or copolymer and the' triazine nucleus, which contains and other a-substituted, nuclearly substituted styrenes, Vinyl naphthalenes, vinyl pyridines, vinyl fluorenes, vinyl dibenzofurans, etc.; allyl, methallyl and other unsaturated monohydric alcohol esters of monobasic acids, e, g., allyl and methyallyl acetates, lauranates, cyanides, etc.; methacrylonitrile, ethacrylonitrileV and other hydrocarbon-substituted acrylonitriles; and numerous other vinyl, acrylic and other compounds containing a single CH2=C grouping which are copolymerizable with acrylonitrile to yield thermoplastic copolymers. Reference is made to the copending application of Henry P. Wohnsiedler and Edward L. Kropa Serial No. 780,296, led concurrently herewith, for additional examples. Alkyl esters of alpha, beta-unsaturated polycarboxylic acids also may be copolymerized with acrylonitrile to yield copolymers which are suitable for use inpracticing the present invention. Examples of-such esters are the dimethyLv-ethyl, -propyL -isopropyl, -butyl, etc., esters of maleic, fumaric, citraconic, mesaconic, etc., acids.- Y

Any suitable method of polymerizing the monomeric acrylonitrile or mixture vof mono-1 mers may be employed. One suitable method is Serial No.v 780,309, also led concurrently here-j with. The polymeric or copolymeric acryloni- For instance, thev at a1o`o111t1'55 Cilinder a' pressure of approximately 3750 pounds per square inch. The molded articles were hard, tough, substantially homoe geneous and had a'good surface appearance. The following test data were obtained on the molded specimens: 1

lbs./in 0.328

Izod impact strength ft.

Flexural strength lbs./sq. in 11,450 Mils flexing (mils exed before'breaking) 25 Dielectric strength at 23.3 C volts/mil 400 Dielectric strength at 100 C do 327 Arc resistance seconds 160 Shrinkage mils per inch '2.7

` Example 2 f A copolymer of acrylonitrile and isopropenyl toluene was prepared by heating under reflux for 40 hours a mixture containing the followingin-L gredients: v f n Y Parts Acrylonitrile 315.0 Isopropenyl toluene ;y 285.0 Water 1520.0 Poiyvinyl alco-hol aqueous "solution) A .52.5 Hydrogen peroxide (30% aqueous solu-l tion) 6.3

Heat-curable melamine-formaldehyde resin 22.5 Acrylonitrile -isopropeny toluene d copoly- 'mer 7.5 Calcined asbestos 45.

The same procedure was followedas described under Example. 1 with the exception .that the time of milling on hot rolls maintained at 110 C. was 1% minutes. The molded pieces were hard, tough, substantially.homogeneous and had agood -surface appearance. The following test data vwere obtained on the molded articles:

I zod .impact strength ft. .lbs./in Mils iiexing 22 Dielectric strength at 25.5 C' Volts/mi1 389 Dielectric strength at 100 C do 328 Arc resistance seconds 160 hrinlagemils per inch` 2 Wx l' 1 g Examplez'., Same as Example 2 w-ithfthe exception that polyacrylonitrile was used in place of the acryf lonitrile-isopropenyl toluene copolymer,A themilling time was 11A; minutes andfthe temperature@ the rolls was 120 C. since the polymer would not soitenat a roll temperature o f-110f C, Hard, toughy-molded" articles "were obtained' The folj- `lowing-'test data were obtainedon the molded pecesr..

Flexural strength lbsl/sq. in 9,980 Milsexing 21 Dielectric strength at 22.2 C Vo1ts/mi1 1412 Dielectric Strengthv at .100 C.. i. .f-do--- 3.98

".:Tr zt '--r @.Qgng-,-

' parts of polyacrylonitrile.

an impalpable powder, 95 parts of heat-curable'. melamine-.formaldehyde resin and 1 part of'zinc stearate (mold lubricant) were -dryiolendepd to" gether for about 30 minutes; and the vblend was then heated on differential. rolls mils.- clearff:y ance between the rolls) for 151/2 minutes. "They slower roll was maintained at a temperature of,I about C. and the faster rollat about130 C; The resulting sheet material was broken and; crushed into granules. Samples of the resulting` unlled moldingcomposition were molded'fo'r 10' minutes at about 155 C. undera pressure. of about 3750 pounds per .square inch. Whenfa molded piece was immersed in boiling water Vfor .'sj'minutes it absorbed. only 0.28% by weight of' water. The'v molded. articles showed improved' flexibility, that is, a lower modulus of elasticity.; as compared with articles similarly made fromf melamine-formaldehyde molding compositions containing no polyacrylonitrile.

Example 5 Same as Example 4 with the exceptionI that 4.151 parts of a slightly Acoarser polyaorylonitrile and" 85 parts of the melamine-formaldehyde resin were used, and the dry blend was heated for 81/2 minutes on differential rolls, the slower one of which was maintained at about Cwhilethe faster one was maintained at about C. The clearance between therolls was dmils. A molde"v ed specimen absorbed only 0.16% byuwoightuof; water when tested for waterabsorptionjas dee scribed under Example 4Q The flexibility of the molded pieceswas slightly better thanV that of the products of Example 4.

" Example 6 One hundred and twenty-two (122) parts of succinonitrle was melted andv poured over 228. The rough blend was transferred to differential rolls. having a clearance of 40 mils. The. blend was milled on the rolls, both of which were maintained at C., for approximately 'rninutes.Y .The charge was slow to soften but gradually became continuous and leathery with a smooth surface grain. The sheet was removed from the-rolls, and., the'i broken and crushed to, pass through ra #einen screen. The screened, plasticizedpolyacrylonif. trile was dried in the oven at .85?. C. for about30 minutes, and was then used in mal ing a molding composition as described below: f ff Parts Heat-curable melamineformaldehyde resin- .769 Succinonitrile-plasticized .polyacrylonitrile 231. Zine'.stearate- +;;;-,--f;;;1i .1-

The aforementioned ingredients were dry blended together forv about. 30 minutes, andthe' blend then" was transferred 'to diiferential'rolls'; the slow roll being heatedl at about 110Cland the 'fast roll at aboutl40 C. Milling on the 'rolls (60 mils clearance between the rolls) was bon-' tinued for 101/2 minutes, after which the material was :removed as.a single sheet J abbut;'.:.1,'inoh thick. The sheet was broken, crushed'into' grain ulesand molded as `described underExarnplffl".v The modulus of elasticity'wasonly' 0.89'asc'm pared with;1.16 and 1.13 for that of moldedartil cles of Examples 4 and 5, respectively.

I.Heat-curable melamine-formaldehyde resins also may be used as a binder for polymers and copolymers. of acrylonitrile. sucna's those herein- 9 before m'entionedwhen the latter are in the for of laments, fibers, threads, yarns, sheets, fabric (woven or matted), or other form. For instance, a laminated article was produced by bonding together superimposed layers of a fabric made from threads of polyacrylonitrile, the fabric having been impregnated with a heat-curable melamineforrnaldehyde resin. The impregnating solution comprised 120 parts oi the melamine resin, 29 parts of 2B alcohol and 60 parts of water. Strips, lil/2 inches by 181/2 inches in size, of the polyacrylonitrile fabric material were immersed in the above solution, dried inair at room temperature and Were then heated for 8 minutes at 115 C. Twenty parts of 50% aqueous alcohol was added to the impregnating solution, and the strips re-dipped and re-dried as above described. The resulting strips were cut into pieces i1/4 dil/i inches in size. A laminate-d article, which contained about equal parts by weight of melamineformaldehyde resin and polyaerylonitrile fabric, was formed by heating the crossed, superimposed layers of impregnated fabric for 59 minutes at 130 C. under a pressure of 1000 pounds per square inch. The laminate had a thickness oi 0.052 inch and an excellent general appearance. It had a dielectric strength at 25 C., between -inch electrodes, or 570 volts per mil. The Values for dielectric constant and dissipation factor, measured at different cycles and at room temperature, are shown below:

Dielectric Dissipatior Cycles Constant Factor Other properties are' shown below in comparison with those of other laminates similarly made frome alpha-paper and canvas:

Canvas Laminate Alphapaper Laminate Polyacrylonitrile Laminate Dynstat flexural strength, kgs.

per sq. om Dynstat bending angle, degrees Dyustat impact strength, kgs.

per se. cm Per cent of wat absorbed after immersion in C. water for 24 hours The hot-moldable (hct-iormable) compositions of this invention may be shaped or formed, as by molding, extruding, calendering, etc., at temperatures ranging, for example, from 130 to 180 C. and at pressures Varying from 1000 to 20,000 pounds or more per square inch. They may be molded4 by cornpression-,l injectionor transfermolding technique. The molding (moldable) compositions show good flow characteristics during molding, and the molded articles are substantially homogeneous throughout and have a good surface appearance. Furthermore, they are tougher and show increased flexibility (lower modulus of elasticity) as compared with molded. articles made from melamine-formaldehyde molding compositions containing no polymeric or copolymeric acrylonitrile modiiier such as is used in practicing our invention. Also, they usually show less shrinkage when molded about inserts M 10 than moldings obtained dfrom unmodified melamine-formaldehyde molding compositions.

Because of the improved flow characteristics of our hot-moldable compositions, they are especially adapted for use in the molding of intricate parts. Thus they may be employed in molding lighting xtures, parts of electrical appliances (including electrically insulating parts), bathroom and other household xtures and ornamental objects, etc. They also may be used in forming surface sheets upon plywood and other laminated articles, and as an overlay for other plastic and other structural materials.

The terms molding and moldable as used herein (including the claims) are employed in a broad sense and are intended to include within their meanings any means of forming or shaping the compositions to which the expressions apply, including molding (in the more limited meaning of the word), calendering, eXtruding or any other means of forming the composition to a desired shape. Likewise, the term molded as used herein has a correspondingly broad meaning.

In our divisional application Serial No. 168,382, iiled June 15,1950, claims are made to a hotmoldable, substantially homogeneous composition comp-rising (i) a heat-curable melamineformaldehyde resin and (2) a thermoplastic copolymer of copolymerizable ingredients including acrylonitrile and a monoVinyl-substituted aromatic hydrocarbon, the acrylonitrile constituting at least about 25% by weight of the total copolymerizable ingredients used in forming the copolymer of (2), and the ingredients of (l) and (2) being present in the said composition in the ratio of, by weight, from about 45 to about 95 parts of the former to from about 55 to about 5 parts of the latter; as well as to products comprising such molded compositions and in which the melamine-formaldehyde resin is in a cured state.

We claim:

l. Composition comprising a resinous melamine-formaldehyde condensation product and a plasticizer therefor consisting of 2.5 parte by weight oi normally solid homopolymerized acrylonitrile to each 22.5 parts of the resinous product.

2. A composition which is moldable under heat and which is asubstantially homogeneous blend of the following ingredients in parts by weight:

Heat-curable melamine-formaldehyde resin- 22.5 Solid, homopolymerized acrylonitrile 7.5 Asbestos 45.0

3. A product comprising the molded composition of claim 2 and in which the melamine-formaldehyde resin is in a cured state.

EDWARD L. KROPA. JOHN P. DUNNE.

REFERENCES CETED vThe following references are of record in the file of this patent:

UNITED s'rA'rEs PATENTS Number Name Date 2,191,581 Nowak et al Feb. 2'7, 1940 2,388,293 Schroy et al. Nov. 6, 1945 2,463,032 .Hanson Mar. 1, 1949 OTHER REFERENCES Pages 80, 81, 89 to 93, Synthetic Resins and Rubbers, by Powers. Published 1943 by John Wiley and Sons, N. Y.

Certificate of Correction Patent No. 2,541,927 February 13, 1951 EDWARD L. KROPA ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 4, line 45, for lauranates read lawl'wtes; column 9, line 28, for

f the word or read of;

'and that the said Letters Patent :should be read as corrected above, so that the same may conform to the record of the ease in the Patent Office.

Signed and sealed this 15th day of May, A.V D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents. 

1. COMPOSITION COMPRISING A RESINOUS MELAMINE-FORMALDEHYDE CONDENSATION PRODUCT AND A PLASTICIZER THEREFOR CONSISTING OF 7.5 PARTS BY WEIGHT OF NORMALLY SOLID HOMOPOLYMERIZED ACRYLONITRILE TO EACH 22.5 PARTS OF THE RESINOUS PRODUCT. 